Search

In this research we prepared nanocrystalline YNbO4:Eu3+ phosphor, i.e. nanophosphor, powder using an efficient mechanochemical method followed by annealing. X-ray diffraction analysis revealed that YNbO4:Eu3+ crystallizes in monoclinic structure C2/c where, from the point of view of A and B in ABO(4) compounds, cation coordination can be noted as [6+2, 4+2]. Crystallite size of about 40 nm, was estimated using Debye Scherrers equation. Raman spectroscopy with 785 and 532 rim excitation wavelengths is performed to record a majority of materials phonon modes and to provide more in depth understanding of the YNbO4 structure. Scanning electron microscopy observations indicate that the mechanical treatment during synthesis is causing non-uniformity of the powder microstructure. High resolution photoluminescent measurements upon UV excitation showed intense emission coming from f-f transitions of the europium ion with the lifetime of 0.68 ms, suggesting that the obtained YNbO4:Eu3+ is a good potential phosphor. A comparison of emissive properties with microcrystalline YNbO4:Eu3+ was made and it showed higher values of emission intensity and lifetime of the nanocrystalline sample.(C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

The aim of this work is to study up-conversion (UPC) luminescence in a series of Tm3+/Yb3+-co-doped GdVO4 samples synthesized by the solid-state method. The concentrations of Yb3+ ions were 3, 6 and 9 mol.%, while the concentration of Tm3+ ions was fixed (3 mol.%). X-ray diffraction patterns for all the synthesized samples confirmed successful formation of a pure GdVO4 phase. Quantitative energy-dispersion x-ray analysis confirmed successful doping of Tm3+ and Yb3+ ions into the GdVO4 matrix. Scanning electron microscope images show that the samples are composed of deformed (irregular) spherical particles with an average diameter size in the range of 1.4-8.4 mu m. Up-converted emission spectra were recorded at room temperature under 980 nm excitation. It was found that all our samples exhibit UPC emission in three different spectral regions: strong emissions are observed at 475 and 800 nm corresponding to the (1)G(4) - GT H-3(6) and H-3(4) - GT 3H6 transitions, respectively, while emission in the red region at about 650 nm is very weak and is due to the (1)G(4) - GT F-3(4) transition. It was concluded that conversion of near-infrared radiation into blue emission proved to be very effective in all the synthesized systems. It was found that emission decay curves for all samples exhibit single exponential behavior.

Rare earth (RE) oxides are important hosts for the luminescence of RE activators with numerous practical applications in light-emitting devices. In this work, we investigated the possibility for Gd2O3: Eu3+ usage in phosphor thermometry by observing the temperature changes of trivalent europium ion transitions from the D-5(0) and D-5(1) energy levels to the ground-state levels. A set of three samples of Eu3+-doped Gd2O3 (1, 5 and 10 at.% Eu3+) was produced via combustion synthesis. The sample crystalline structure is confirmed by XRD measurements. The intensity ratio of the two emission lines was studied as a function of temperature in the temperature range 300-800 K, and lifetime was measured in the interval 10-800 K. All three Gd2O3: Eu3+ samples proved to have good potential for the development of thermographic phosphors.

Over the past few years, rare-earth-ion-doped materials have attracted a great deal of interest due to their potential application as optical temperature sensors. The luminescence properties of these materials are sensitive and change with temperature. Here, we have investigated the properties of yttrium oxide powder co-doped with Yb3+ and Er3+, synthesized through the spray pyrolysis method at 900 degrees C and additionally thermally treated at 1100 degrees C for 24 h. The structural and morphological characterizations are carried out through x-ray powder diffraction (XRPD) and scanning electron microscopy (SEM). The obtained particles are spherical in shape and have cubic bixbyite structure with the space group Ia-3. Photoluminescent measurements (PL) are recorded in the temperature range from 10 to 300 K using 978 nm radiation. Emission spectra are assigned to the following trivalent erbium f-f electronic transitions: H-2(9/2) - GT I-4(15/2) (blue: 407-420 nm), (H-2(11/2), S-4(3/2)) - GT I-4(15/2) (green: 510-590 nm) and F-4(9/2) - GT I-4(15/2) (red: 640-720 nm). The fluorescent intensity ratios of the blue, green and red areas under emission bands show significant temperature sensitivity, with the largest value of 2.3 K-1.

We prepared an efficient YNbO4:Eu3+ phosphor using a simple solid-state reaction method and examined its photoluminescent properties in order to investigate the possibility for its usage in phosphor thermometry. Photoluminescence measurements were performed in the temperature range 303-803 K, and the fluorescence intensity ratio (FIR) of the paired emissions lines of Eu3+ (D-5(1) - GT F-7(1) and D-5(0) - GT F-7(1) transitions) was studied as a function of temperature. The sample crystalline structure is confirmed by XRD measurements. The material is proved to have a good potential for the development of thermographic phosphors. It exhibits maximum temperature sensitivity of approximately 3.5 x 10(-3) K-1 in the temperature region around 700 K. (C) 2013 Elsevier Ltd. All rights reserved.

Herein, temperature dependencies of emission and emission decay of Zn2SiO4:Mn2+ powder in the range from room temperature to 300 degrees C is reported. These dependencies allow temperature sensing from luminescence measurements, since Mn2+ emission intensity, emission band spectral position, and emission decay are rapidly changing over the entire temperature range. For fluorescence intensity ratio method, measurement that relays on emission intensity changes with temperature, sensitivity of 12.2% is found. In the case of lifetime thermometry, method that relays on emission decay changes with temperature, sensitivity of 0.48% is determined. Both sensitivity values are among the highest ever recorded for inorganic materials. (C) 2013 AIP Publishing LLC.

Phosphors are thermographic if their emission characteristics change with temperature. In this paper, we investigated the potential use of a europium-doped (1, 3 and 6 at.% Eu3+) yttrium-gadolinium oxide (Y0.75Gd0.25)(2)O-3 nanostructured matrix for phosphor thermometry and thermometry in high-energy radiation fields. Photoluminescence emission measurements were recorded in the temperature range from room temperature to 873 K, observing temperature changes in trivalent europium ion transitions from D-5(1) and D-5(0) energy levels. The results show that Eu3+-doped (Y0.75Gd0.25)(2)O-3 is a new promising high-temperature thermometric phosphor with a very good sensitivity of approximately 4.9x10(-3) K-1 at 823 K for a sample doped with 1 at.% Eu3+. It is shown that with this material the fluorescence intensity ratio method can be used for temperature measurements in high-energy radiation fields without the use of an optical excitation source. In this case a maximal sensitivity of 2.35x10(-3) K-1 is obtained.

Rare-earth orthovanadates are important hosts for the luminescence of rare earth activators with considerable practical applications in the artificial production of light. In this paper we investigated the possibility for GdVO4:Sm3+ usage in phosphor thermometry by observing the temperature changes of trivalent samarium transitions from F-4(3/2) and (4)G(5/2) energy levels to the ground state. A set of three samples of Sm3+-doped GdVO4 (0.5, 1 and 2 mol.% Sm3+ with respect to Gd3+ ions) was produced via solid state synthesis. The sample crystalline structure is confirmed from x-ray diffraction (XRD) measurements. Photoluminescence measurements were recorded in the temperature range 293-823 K and the fluorescence intensity ratio of the paired emissions bands was studied as a function of temperature. All three GdVO4:Sm3+ samples proved to have good potential for the development of thermographic phosphors, whereas the maximum sensitivity of approximately 4.5x10(-4) K-1 was found for the sample with 2 mol.% Sm3+ in the temperature region around 750 K.

Samarium doped LaYO3 nanocrystalline phosphor powders are obtained by polymer complex solution method. Stoichiometric quantities of La2O3, Y2O3 and for dopant ions Sm2O3 were dissolved in hot nitric acid. Polyethylene glycol was added in solutions in 1:1 mass ratio to corresponding metal nitrates to form gel. The gel is combusted and annealed at 800 degrees C for two hours to form nanopowder samples. Crystalline structure and phase purity is checked by X-ray diffraction and show that this material is synthesized in cubic bixbyite type structure for the first time. Luminescence properties of Sm3+ doped LaYOL3 exhibited characteristic orange-red emission coming from the intra-4f-shell (4)G(5/2) - GT H-6(J) electron transitions with emission decay of 1.5 ms. Energy level positions are derived from emission and excitation spectra.

Lithium-indium oxide is one of the candidate materials as solid-state scintillators for solar neutrinos due to an inverse beta -decay of In-115 to Sn-115. On the other hand, when doped with rare-earth ions such as Eu3+ or Sm3+, it becomes a promising phosphor material. In this report we present a simple solid-state procedure for preparation of LiInO2:Eu3+ powders. X-ray diffraction confirmed product in tetragonal structural form (space group: I4(1)/amd) and no impurity phases were detected. Then, high resolution photoluminescence emission measurements were performed at room and low temperatures to find D-5(0) - GT F-7(J). Emission kinetics from D-5(0) level exhibited pure single exponential behavior with lifetime of about 1.5 ms. Maximum energy splitting of F-7(1) manifold is recorded as a function of temperature. (C) 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim